Auckland Transport and police are discussing possible live video feeds from the city's new electric trains to combat soaring vandalism.
A monthly repair bill of about $50,000 is triggering a review of how on-board CCTV cameras can be used more effectively.
A 17-year-old is awaiting court sentencing after being identified among five youths who allegedly defaced 22 windows and the backs of 20 seats inside four minutes between Glen Innes and Panmure.
But the others have yet to be caught, raising a prospect of police and Auckland Transport monitoring live feeds from trains on high-risk sectors, rather than having to trawl through video files after offenders have fled.
Although offending around stations can be viewed on screens at a traffic management centre on Queens Wharf, "real-time" surveillance has yet to be extended to the 12 CCTV cameras inside each three-car electric train.
That is believed to be under consideration for crime-fighting protocols being negotiated by Auckland Transport, train operator Transdev, police and others.
Although spray cans and rocks cause the most visible damage, hurled eggs also create problems once dry.
Tags etched into seat backs and windows are another bugbear. Protective film can be peeled off the double-glazed windows and replaced for about $100 a time.
But seat backs have to be sent away for repair, prompting Auckland Transport to consider attaching film to them as well.
An audit last month found 15 per cent of seat backs throughout the electric fleet had been scratched or gouged with sharp objects, and half the windows in one carriage the Herald was invited to inspect were etched into.
Electric trains integration manager Allan Gordon said an escalation in damage since the new fleet started running full-time on the southern rail line to Papakura was running down seat back stocks.
Although a gallery of suspects is being compiled, a big challenge is to put names to faces. That should become easier once new legislation is introduced next year to require fare evaders to provide names and addresses to council-appointed enforcement officers, or face fines of up to $1000.
Auckland Transport chairman Lester Levy says fare evasion often goes hand-in-hand with other anti-social behaviour.